Method and means for hindered settling classification



Feb. 8, 1949. m. BITZER METHOD AND MEANS FOR HINDERED SETTLINGCLASSIFICATION 2 Shasta-Sheet 1 Filed Apfil 21; 1944 EnMwvn a. BITZERINVEN TOR.

ATTORNEY- Feb. 8, 1949. E. c. BITZER 6 METHOD AND MEANS FOR HINDEREDSETTLING CLASSIFICATION 2 Sheets-Sheet 2 Filed April 21, 1944 EDMUYVDC".- BITZER INVENTOR.

BY Y 44% AT TORNL'Y Patented Feb. 8, 1949 METHOD AND MEANS FORHINDERIilD SETTLING CLASSIFICATION Edmund C. Bitzer, Golden, Colo assignor to Colorado Iron Works Company, Denver, 0010., a corporation ofMaine Application April 21, 1944, Serial No 532,180

This invention relates to hydraulic classification means and methods,and more particularly relates to a novel type of hindered settlingclassification applicable to various types of conventional mechanicalclassifying apparatus.

Most wet, classification of ores or similarly finely divided solids suchas sand, cement mix etc. is practiced in mechanical classifiers. Thistype of machine comprises an inclined tank or trough which whensubstantially filled with a pulp comprising a mixture of water andmaterial to be classified forms a pool at the lower end of the tank.Classification is accomplished by inducing the larger and heavierparticles of the feed to settle while the lighter and finer particles ofthe feed are maintained in suspension and removed from the tank byoverflow. The settled solids, commonly called the sand product, areremoved from the tank by conveying them up the sloping bottom under theaction of the mechanical means which may consist of revolving helicalblades or spiral assembly, reciprocat- 7 ing rakes or a continuous chaindrag.

As the settled material passes the upper limit of the pool, the finesolids and water begin to drain out on the sloping bottom and fiow backinto the pool. In this way, the elevating mechanism acts both as aconveyor and a dewatering device. Most classification treatments aredirected toward control of the size distribution of particles in theoverflow, with the object of maintaining a set minimum amount of what isclassed as oversize material. The amount and size range of thisso-called oversize varies within wide limits depending upon therequirements of a given operation. V

In most apparatus the entering feed is delivered to the classifier nearthe upper limits of the pool. The larger particles of oversize plus aproportion of what could be accepted as overflow material settle out assoon as they enter the pool and thereafter are conveyed up the slopingbottom. Smaller particles of oversize settle out of suspension as thepulp flows back from the feed inlet to the overflow weir, and the objectof the conventional operation is to control the settling rate of theoversize in such manner as to settle everything coarser than a certainpredetermined size before the pulp stream reaches the overflow point.

By operating in this manner, a varying but substantial amount ofacceptable overflow material settles or is entrained with the largeroversize material and in conventional practice, little, if anything, canbe done to prevent the 1': Claims. (Cl. 209-l8) 2 settling of thisacceptable material without causing an undesirable amount of largeparticles to pass out with the overflow. As a result, such operationsare ineflicient in varying degrees, depending upon the amount ofacceptable material that settles or is carried into the oversize sands.

In present practice, the principal method of controlling the size of theclassifier overflow product is to regulate the specific gravity of themixture of solids in liquid, usually water, by controlling the additionof fresh liquid to the pool. In general, fine overflows are made by theaddition of fresh liquid in large quantity or volume and maintaining lowpulp gravities, while coarse overflows are made by reducing the freshliquid introduction and allowing the specific gravity of the pulp toincrease. Another important factor in the control is the amount ofextremely fine material, generally designated slimes, in the classifierfeed.

When the slimes content is slight or entirely lacking, the operation ismuch more difiicult to control because the settling rate of solids is sohigh that far too much acceptable overflow material settles with theoversize. Control by means of fresh liquid introduction in such cases isnot effective, and particularly when the object is to make a coarseoverflow, the present type mechanical classifiers fail to performsatisfactorily. I

It will be noted from the foregoing that in their conventional methodsof operation, the mechanical classifiers heretofore in use are requiredto convey, dewater and classify in a single tank under conditions whichcause the conveying and dewatering functions to interfere with theprimary treatment, namely, that of A further object of the invention isto provide a a method of classification which may be utilized in theconcentration of an ore constituent rather than providing the usual sizeclassification of' ore constituents.

ing pools, with the pool in which the solids and liquids are initiallyfed being. maintained free from the influences ofthe conveying anddewatering mechanism, and utilizing the second pool in which theconveying and dewatering steps are performed to provide a resistancefactor exerted against the first said pool to impede the settling ofsolids therein.

The invention will be best understood by reference to the accompanyingdrawings which illustrate typical structural embodiments for practicingthe novel treatment. In the drawings in the several views of whichlikeparts have been designated similarly,

Fig. 1 is a fragmentary side elevation partially broken to showessential features of the various treatment stages; I

Fig. 2 i a fragmentary top plan view of the classifier tank shown inFig. 1, with the spiral conveyor and feed box removed to betterillustrate the relation of the treatment stages;

Fig. 3 is a fragmentary side elevation of another form of treatment tankembodying features of the present invention and partially broken to showdetails of the treatment stages;

Fig. 4 is an enlarged section through one of the liquid injectingnozzles; and

Fig. 5 is an enlarged top plan view of the classification compartment ofthe tank shown in Fig. 3.

Referring first to the form of the invention shown in Figs. 1 and 2, aclassifier of the Akins or spiral conveyor type has been illustratedwith features of the present invention applied thereto.

This classifier comprises an elongated tank 6 suitably supported withits bottom I in an inclined position. At the lower end the interior oftank 6 is divided by a partition member designated generally by thenumeral 8 into two pools P and P'. Th e pool P is enclosed by a slopingbottom member 9, an adjustable overfiow weir I and side walls 6a of tank6. The bottom member 9 is suitably apertured as indicated at I2 andsupports at spaced intervals a plurality of pipes or conduits l3suitably apertured as indicated at M in Fig. 2, to function as injectionnozzles. Liquid is delivered to the nozzles 3 through a valve-controlledsupply line l and a hutch box IE mounted on the under surface of slopingbottom 9. Preferably, an overflow box I! adjoins the adjustable weir l0and is provided with a suitable outlet nipple It for attachment of anysuitable conduit member.

This unit comprises the primary classification zone or compartment C,while the portion of the tank interior on the opposite'side of partition8 together with its associated mechanism constitutes the conveying anddewatering zone or compartment D.

Feed to pool P preferably is delivered through an adjustable feed box20, the outlet of which is submerged in pool P'. The partition member 8in the preferred form comprises a lower section 8.1:, which is fixedlyheld in tank 6 in supporting relation to the sloping bottom member 9.The upper section 811 is mounted for up and down movement in spacedrelation to section 8.1: to provide an outlet passage 2| of restrictedcharacter but of variable dimension. -The restriction of opening 2| andthe extension of the member 811 to a point substantially higher than theoverflow level determined by the top surface of weir l0 results in thecreation and maintenance of a liquid level for pool P which issubstantially higher than the level of pool P whenever additional liquidis supplied to the pool, as clearly shown in Fig. 1.

This' superelevation is utilized in the operation of the apparatus tocause a back fiow through in a manner well known in the art.

tion, the operations performed in such apparatus Preferably, there isprovided on-the bottom of tank I one or more wash boxes 24 positioned toact on the solids being elevated by conveyor 22 and wash therefrom fineparticles which have been entrained in or otherwise intermingled withthe coarse particles. Also in the preferred construction, a liquid inletin the form of'a pipe 25 is supported in overhanging relation to pool Pand preferably has its discharge outlet in close proximity thereto toavoid undue turbulence in the discharge of liquid into the pool.

With-this understanding of the construction required in adaptingclassifiers of the spiral conveyor type to the practice of the presentinvenwillnow be described. Pulp is introduced through inlet 20 andinitially fills the tank to the effective level of weir In asestablished by the number ofslat membersforming the weir. In thisoperation a portion .of the pulp passes through the opening 2| and thespiral assembly 22 is ro'tatedby shaft 23 to move settled sands upwardlyalong the tank bottom to the point of discharge' Prior to or as soon asthe levels on opposite sides of partition 8 are uniform, liquid underpressure is admitted to hutch box'lB through the valve-controlledconduit l5 and thence is discharged in jets or fine streams through thenozzle members Hi to keep the mass of pulp constituting pool P' inteeter, and at the same time to induce an upward movement of fineparticles through the downwardly descending mass of coarse particles. 4

At the same time the pulp in pool P is diluted by the introduction ofadditional liquid through wash boxes 24 or inlet 25, or both, and solong as the amount of liquid so introduced is in a volume in excess ofthe volume that will pass through the restricted opening 2| and risethrough the dense liquid body forming pool P' to pass across overflowweir Ill, the level of pool P will rise progressively. Whenever thedesired super-elevation has been attained, the liquid introduction intopool P through wash boxes 24 and feed inlet 25 is reduced to balance theoutflow through passage 2| and thereafter a substantially static leveldifferential is maintained.

55 I While this condition maintains, there is a continuous 'diow offluid from pool P into pool P which is countercurrent to the travel ofcoarse particles settling through pool P' under gravitadrain back intopool P as a liquid suspension of greater density than the liquidsuspension-medium of the pool. The resulting increase in density of thepulp forming pool P provides additional resistance to the settlingparticles approaching opening 2|, with the result that only particles ofrelativelycoarse size are able to overcome the combined resistancefactors in pool P and pass out of such pool into pool P, while otherparticles of relatively coarse but lesser size are impelled to thesurface by the combined resistance factors and pass from the pool P byoverflow. The ultimate result of this action is that in this classifyingtreatment a much coarser overflow product is obtained than hasheretofore been possible by using the conventional methods of mechanicaltype classifiers.

In certain treatments the settling area provided by compartment C may betoo large to permit the operation to overflow a product of the desiredcoarseness. An effective method for attaining the desired resultis totreat the same volume of feed in a smaller settling area, which changedcondition tends to increase the density of the pulp and thereby impedethe settling of larger sized particles to increase the size of theoverflow product. Such a change is readily effected by inserting one ormore partitions 26 as shown in Fig. 2, which reduce the size of thesettling area in compartment C.

From the foregoing it will be apparent that a classifier of the typeillustrated in Fig. 1 provides two physically separated butintercommunicating pools lying generally in the same horizontal plane,with the pool into which the initial feed is delivered being maintainedsubstantially free from the conveying and dewatering influences of theother pool, but subject to a hydrostatic head therein exerted throughthe communicating passage. Also in said second pool the conveying anddewatering steps preferably are performed in conjunction with liquidintroduction which serves to create an increased density factor in thewhich may be operated to overflow a product much coarser than hasheretofore been possible in the operation of conventional typemechanical classifiers.

In Figs. 3, 4 and 5, the features of the present invention have beenshown as applied to a classifier of a reciprocating rake type. Thisappara-. tus comprises a rectangular tank 46 suitably sup:

portedto dispose its bottom 41 at a substantial. inclination and having'its interior divided by a partition member 48 into a classificationcome. partment C and a conveying and dewatering compartment D. I

The end wall 48 of tank 46 acts as thesloping bottom of compartment C'and terminates at (its upper end in a slat weir 50 or similarregulatingmeans for varying the overflow level. A plurality. of nozzlemembers 53 are mounted at intervals along sloping bottom 49, each ofwhich is provided with a series of apertures 64 for the discharge ofliquid.

The nozzles 53 are loosely held in U-clamps It and may be turned, asfrom the full line position of opening 54 to the dotted line position,for example, to direct the discharge. through said openings in differentdirections in compartment C. A header 55 carries a'supply of liquidunder pressure and a flexible conduit 56 connects each individual nozzlemember 53 with said header and has a valve 51 .to permit selectivecontrol of w the discharge velocity.

Pulp is fed into compartment C through a feed box 60 and upon dischargeis subjected to the elevating influence of the jets issuing from nozzles53, which are individually regulated for compartment pass through anopening 8| in partition 48 and enter compartment D. In the lattercompartment, the settled solids are moved upwardly along sloping bottom41 by reciprocating rakes 62 actuated by mechanism 83.

Preferably the raked solids are subjected to the action of one or morewash boxes 64, which are subject to individual valve regulation asindicated at B5 in Fig. 3. Again in this form the addition of waterthrough wash boxes, 64 and the restriction to discharge provided byopening. 8i serve to create a superelevation of the pulp body P incompartment D relative to the. pool P in compartment C. The size of theopening and the height of superelevation determine the velocity ofliquid passing through the slot and as the sinking particles must passcounter to this stream to enter pool P, a classification according tosize, shape or specific gravity takes place.

In the classification compartment C, an increase of jet pressure willresult in the removal of coarser particles from the mass of pulp andtheir overflow from the compartment, whereas a decrease in jet pressureresults in the removal and overflow of finer particles. In addition tothe control provided :by jet pressure, the direction of the jets affectsthe rising currents and surface movements and thus is another factor inthe control of particle size in the overflow.

From the foregoing description of the construction and operation of theclassifiers illustrated in Figs. 1 and 3, it will be apparent that suchfeatures are generally applicable to various types of mechanicaltype-classifiers such as chain drag'classiflers (not illustrated) orvarious reciprocating rake type such as the form shown in Fig. 3, or tovarious spiral or Akins type as shown in Fig. 1. Similarly, the novelfeatures of Fig. 1 may be incorporated in the classifier of Fig. 3 andconversely the novel features of Fig. 3 may be incorporated in theclassifier of Fig. 1. This applies particularly to the liquid injectingnozzles f the classification compartment, which may either a fixed typeof an adjustable type and which may be regulated by only one valve or byhaving each nozzle individually regulated by its own valve.

The wash boxes may be located with their -a,seo,eo1 4 w upper surfacesabove the tank bottom as shown 7 in Fig. 1. or may be beneath the tankbottom which, in such case, is suitably apertured to admit the liquidfrom such wash boxes.

The partition dividing the classification compartment from the conveyingand dewaterlng compartment may be a single wall suitably slotted toprovide the connecting passages, in

is attached by welding to convert such standard classifier to thepractice of the present invention. In suchconverslon the wash boxes 24also may be installed in conventional tank designs. The wash box per sehas been shown and described in the co-pending application of Thomas A;Dickson, Serial No. 471,989, now- Patent No. 2,428,789, Oct. 14, 1947,and features described but not claimed herein have been made thesubjects matter of claims in said application. Another feature of theoperation performed in the various forms of classifiers described andclaimed herein is that the resistance factors to the settling ofparticles in the classification compartment may be maintained to efiecta separation according to specific gravity rather than according to sizeor shape. As an example, if a given ore contains one or more minerals ofhigh specific gravity and associated rock or gangue matter of relativelylow specific gravity,

the impedance to settling in the classification compartment may beestablished to cause substantially all the gansue matter regardless ofits size or shape, to pass out across the overflow while the mineralthrough the various size ranges, because of its high specific gravity,will settle through the resistance zone and pass into the conveying anddewatering compartment claims.

What I claim and desire to secure by Letters Patent is:

l. A hydraulic classification method, which comprises the treatment of abody of solids in mixed sizes in two pools which lie within a commonhorizontal plane and in adjoining vertical planes maintained inphysically separated relation with a countercurrent restricted flow fromthe bottom of one said pool into the bottom of the other pool, one ofsaid pools having its surface at a substantially-higher elevation thanthe surface of the other pool, feeding a pulp containing solids in mixedsizes intoone said pool at a point horizontally distant and at a higherelevation thanthe restricted flow, maintaining a hindered settlingaction in the pool in which the pulp is fed by directing upward flowingcurrents across substantially the entire area of the pool between thepoint of feed introduction and said restricted flow,- passing'solids inthe larger size ranges countercurrent to said upward currents in ahorizontally ranging course into and through the restricted flow to theother said pool, feeding wash water into the conveying 'pool'at a ratesuilicient to maintain the level of the conveying pool above the levelof the first mentioned pool, flowing the wash water containing fineparticles from the conveying pool to the first mentioned pool forfurther impeding said countercurrent settling conveying settled solidsthrough said lastmentioned pool to an elevated point of discharge,-

and overflowing solids in the finer size ranges from the first saidpool.

2. A hydraulic classification method, which comprises the treatment of abody of solids in mixed sizes in two pools which lie within a commonhorizontal plane and in adjoining verticalplanes maintained inphysically separated relation with a countercurrent restricted flow fromt e bottom of one said pool into the bottom of the other pool, one ofsaid pools having its surface at a substantially higher elevation thanthe surface of the other pool, feeding a pulp containing solids in mixedsizes into one said pool at a point horizontally distant and at a higherelevation than the restricted flow, maintaining a hindered settlingaction in the pool in which the pulp is fed by directing upward flowingcurrents across substantially the entire area of the pool between thepoint offeed introduction and said restricted flow, moving said currentsthrough the pool at a velocity sufllcient to maintain the contents ofthe pool in constant teeter, passing solids in the larger size rangescountercurrent to said upward currents in a horizontally ranging courseinto and through the restricted fiow to the other said pool, feedingwash water into the conveying pool at a rate sufilcient to maintain thelevel of the conveying pool above the level of the first mentioned pool,flowing the wash water containing fine particles from the conveying poolto the first mentioned pool for further impeding said countercurrentsettling conveying settled solids through said last-mentioned pool to anelevated point of discharge, and overflowing solids in the finer sizeranges from the first said pool.

3. A hydraulic classification method, which comprises the treatment oftwophysically separated pools confined in end-to-end relation, oneofwhich has its surface at a substantially higher elevation than thesurface of the other pool, feed- .ing a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in which the pulp-is fed through a zone ofrestricted volume into the lower portion of the other said pool,

directing upward flowing;.currents substantially across the bottom ofthe pool in which pulp is fed to hinder settling of fine sizes in thefeed, feeding wash water into said other pool at a rate sufiicient tomaintain the level of said pool above the level of the pool into whichthe pulp is fed, said wash water forming a high density fluid withsolids of the finer size ranges flowing the high density fluid from thepool of higher surface elevation into the zone of restricted volume soas to further impede the settling of particles in fine sizes in theother pool, overflowing solids in the finer size ranges from thelast-mentioned pool, and conveying settled solids through the pool ofhigher surface elevation to an elevated point of discharge from thetreatment.

4. A hydraulic classification method, "which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one orwhich has its surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in which the ,pulp if fed through a zone ofrestricted volume into the lower portion of the other .said pool,directing upward flowing currents substantially across the bottom of thepool in which pulp is fed to hinder settling of fine sizes in the feedby 10 to further impede the settling of particles in fine sizes in theother pool, overflowing solids in the finer size ranges from thelast-mentioned pool,

conveying settled solids through the pool of higher surface elevation toan elevated point of discharge from the treatment, and subjecting solidsbeing conveyed out or said pool to a washing action to remove entrainedfines and thereby increase the density of the pool into which theydrain.

7. A hydraulic classification method, which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one ofwhich has its surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in which the pulp is fed through a zone ofrestricted volume into the lower portion of the other said pool,

directing upward flowing currents in different 3directions'substantially across the bottom of the overflowing solids inthe finer size ranges from the last-mentioned pool, and conveyingsettled solids through the pool of higher surface elevation to anelevated point of discharge from the treatment.

5. A hydraulic classification method, which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one

. of which hasits surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in pool in which pulp is fed to hindersettling of fine sizes in the feed, feeding wash water into said otherpool at a rate sufiloient to maintain the level of said pool above thelevel of the pool into which the pulp is fed, said wash water forming ahigh density fluid with solids of the finer size ranges flowing the highdensity fluid from the of streams therein, feeding wash water into saida high density fluid with solids of the finer size ranges flowing thehigh density fluid from the pool of higher surface elevation into thezone of restricted volume so as to further impedethe settling ofparticles in fine sizes in the other pool, overflowing solids in thefiner size ranges from the last-mentioned pool, and conveying settledsolids through the pool of higher surface elevation to an elevated pointof discharge from the treatment.

6. A hydraulic classification method, which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one ofwhich has its surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the poolin which the pulp is fed through a zone ofrestricted volume said wash water forming 'a high density fluid' withsolids of the finer size ranges flowing the high density fluid from thepool of higher surface elevation into the zone of restricted volume soas pool of higher surface elevation into the zone of restricted volumeso as to further impede the settling of particles in fine sizes in theother pool,

overflowing solids in the finer size ranges from the last-mentionedpool, and conveying settled solids through the pool of higher surfaceelevation to an elevated point of discharge from the treatment.

8. A hydraulic classification method, which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one ofwhich has its surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in which the pulp is fed through a zone ofrestricted volume into the lower portion of the other said pool,

directing upward flowing currents substantially across the bottom of thepool in which pulp is fed to hinder settling of fine sizes in the feed,

feeding wash water into said other pool at arate sufilcient to maintainthe level of said pool above the level of the pool into which the pulpis fed, said wash water forming a high density fluid with solids of thefiner size ranges flowing the high density fluid from the pool of highersurface elevation into the zone of restricted volume so as to furtherimpede the settling of particles in fine sizes in the other pool,overflowing solids in the finer size ranges from the last-mentionedpool, conveying settled solids through the pool of higher surfaceelevation to an elevated point of discharge from the treatment, andincreasing the density of the pulp in the last-mentionedpool to provideadditional resistance to the passage of solids from the other pool.

' 9. A hydraulic classification method, which comprises the treatment oftwo physically separated pools confined in end-to-end relation, one ofwhich has its surface at a substantially higher elevation than thesurface of the other pool, feeding a pulp containing solids in mixedsizes into the pool of lower surface elevation, flowing settled solidsfrom the bottom of the pool in which the pulp is fed through a zone ofrestricted volume water forming a high density fluid with solids of theflner size ran es flowing thehigh density fluid from the pool of highersurface elevation into the zone of restricted volume so as to furtherimpede the settling of particleain fine sizes in the other pool,overflowing solids in the liner size.

ranges from the last-mentionedpool, and conirom the treatment.

10. Apparatus of the character described, conprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end ofsaid inclined bottom, an overflow weir at the lower end of said tank, apartition dividing said tank into two compartments for maintaining.

pulp-containing pools in end-to-end relation, there'being a restrictedopening in said partition for the countercurrent passage of pulp fromthe bottom of one pool to the bottom of the other, means for feedingpulp into the compartment adjoining said overflow weir, said compartmenthaving its bottom disposed in converging relation to the partition atthe restricted opening so as to crowd and direct settling solids throughsaid 1 opening, means for injecting liquid under pressure in a pluralityof streams distributed over substantially the entire bottom of thefeedreceiving pool, and conveyor means for moving settled solids in theother said compartment to the solids discharge outlet.

11-. Apparatus of the character described, comprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end of-said inclined bottom, an overflow weir at the lower end of said tank, apartition dividing said tank into two compartments for maintainingpulp-containing pools in end-to-end relation,

there being a restricted opening in said partition for thecountercurrent passage of pulp from the bottom of one pool to the bottomof the other,

means for feeding pulp into the compartment adjoining said overflowweir, said compartment having its bottom disposed in converging relationto the partition at the restricted opening so as to crowd and directsettling solids through said opening, means for injecting liquid underpressure in a plurality of streams distributed over substantially theentire bottom of the feedreceiving pool, said means being 'mounted formovement to different liquid injecting positions, and conveyor means formoving settled solids in the other said compartment to the solidsdischarge outlet.-

12. App ratus of the character described, comprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end'of said inclined bottom, an overflow weir at the lower end of saidtank, a partition dividing said tank into two compartments formaintaining pulp-containing pools in end-to-end relation, there being arestricted opening in said partition for the countercurrent passage ofpulp from the bottom of one pool to the bottom of the other, means forfeeding pulp into the compartment adjoining said overflow weir, saidcompartment veying settled solids through the pool of higher surfaceelevation to an elevated point of discharge having-its bottom disposedin converging relation to-the partition at the restricted opening so asto crowd and direct settling solids through said opening, means forinjecting -liquid under pressure in a plurality of streams distributedover substantially the entire bottom of the feedreceiving pool, meanscomprising at least one partition arranged to vary the width of thefeedreceiving pool, and conveyormeans for moving settled solids in theother said compartment to r the solids discharge outlet.

13. Apparatus of the character described, comprising a tank for pulphaving an'inclined bottom, a solids discharge outlet at the upper end ofsaid inclined bottom, an overflow weir at the ,lower end of said tank, apartition dividing said tank" into two compartments for maintainingpulp-containing pools in end-to-end relation, there being a restrictedopening in said partition for the countercurrent passage of pulp fromthe bottom'of one pool to the bottom of the other, means for feedingpulp into the compartment adjoining said overflow weir, said compartmenthaving its bottom disposed in converging relation to the partition atthe restricted opening so as to crowd and direct settling solids throughsaid opening, 'means for injecting liquid under preslower end of saidtank, a partition dividing said 40 tank into two compartments formaintaining pulp-containing pools in end-to-end relation, there being arestricted opening in said partition for the countercurrent passage ofpulp from the bottom of one pool to the bottom of the other, means forfeeding pulp into the compartment adjoining said overflow weir, saidcompartment having itsbottom disposed in converging relation to thepartition at the restricted opening so as to crowd and direct settlingsolids through said opening, means for injecting liquid under pressurein a plurality of streams distributed over substantially the entirebottom of the feed-receiving pool, including a plurality of nozzlesdisposed along said sloping bottom at intervals above the opening and anindividual valve-controlled conduit connected to each said nozzle, andconveyor means for moving settledsolids in the other said compartment tothe solids discharge outlet.

15. Apparatus of the character described, comprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end ofsaid inclined bottom, an overflow weir at the lower end of said tank, apartition dividing said tank into two compartments for maintainingpulp-containing pools in end-to-end relation, said partition comprisinga lower portion fixedly held within the tank and an upper portionmounted to provide a restricted passage of variable area for thecountercurrent passage of pulp from the bottom of one pool to the bottomof the other, means for feeding pulp into the compartment adjoining saidoverflow weir, said compartment having its bottom disposed in convergingrelation to the partition at the restricted opening so as to crowd 13means for injecting liquid under pressure in a plurality of streamsdistributed over substantially the entire bottom of the feed-receivingpool, conveyor means for moving settled solids In the other saidcompartment to the solids discharge outlet, and means for supplyingadditional liquid to the pulp body in the last-mentioned compartment.

16. Apparatus of the character described, comprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end ofsaid inclined bottom, an overflow weir at the lower end of said tank, apartition dividing said tank into two compartments for maintainingpulp-containing pools in end-to-end relation, said partition comprisinga lower portion fixedly held within the tank and an upper portionmounted for up and down movement to provide a, restricted passage ofvariable area for the countercurrent passage of pulp from the bottom ofone pool to the bottom of the other and extending above the elevation ofthe overflow weir to provide a superelevation of the pool adjoining thesolids discharge end of the tank, means for feedlng pulp into thecompartment adjoining said overflow weir, said compartment having itsbottom disposed in converging relation to the partition at therestricted opening so as to crowd and direct settling solids throughsaid opening, means for injecting liquid under pressure in a pluralityof streams distributed over substantially the entire bottom of thefeed-receiving pool, conveyor means for moving settled solids in theother said compartment to the solids discharge autlet, and means forsupplyingadditional liquid :0 the pulp body in the last-mentionedcompartment.

17. Apparatus of the character described, comprising a tank for pulphaving an inclined bottom, a solids discharge outlet at the upper end ofsaid inclined bottom, an overflow weir at the lower end of said tank, apartition dividing said tank into two compartments for maintainingpulp-containing pools in 'end-to-end relation, there being a restrictedopening in said partition for the countercurrent passage of pulp fromthe bottom of one pool to the bottom of the other, means for varying therestriction of said opening, means for feeding pulp into the compartmentadjoining said overflow weir, said compartment having its bottomdisposed in converging relation to the partition at the restrictedopening so as to crowd and direct settling solids through said opening,means for injecting liquid under pressure in a plurality of streamsdistributed over substantially the entire bottom of the feedreceivingpool, and conveyor means for moving settled solids in the other saidcompartment to the solids discharge outlet.

EDMUND C. BITZER.

REFERENCES .CITED The following references are of record in the file ofthis patent:

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